Astaxanthin is known as a red carotenoid which has a wide distribution in crustaceans such as krill, shrimp, crab and the like, the body surface of porgy, the muscle of salmon, fish eggs such as salmon roe and the like, in yeast, algae or genetic recombined microorganisms. Astaxanthin is used as a color tone-improving agent and reviver for cultivated fishes and shellfishes and it is also reported to act as an antioxidant, etc. (Enju Shimizu and Wataru Miki: “Carotinoids of Marine Organisms”, edited by Wataru Miki, Koseisha Koseikaku in the 5th year of Heisei) and has been applied to food additives, cosmetics and so on. This astaxanthin can be obtained from plants, genus Falfa yeast cell body, seaweeds, bacteria, or crustaceans by extraction techniques. Particularly, a process for obtaining astaxanthin from the green algae of Haematococcus is in an extremely advantageous position as a process for supplying astaxanthin derived from a natural origin since there was developed a process for cultivating Haematococcus containing a high concentration of astaxanthin in large quantities and stably. Some processes are reported for extracting astaxanthin from this Haematococcus alga. Usually, this Haematococcus is covered with the cell walls enclosed by a gelatinous and sticky capsule, and hence the cell walls of the algae are ruptured (broken) for the purpose of extracting astaxanthin. As one of the processes for rupturing (breaking) the cell walls of the alga, the process for subjecting the algae to physical rupture treatment is known. Specifically, the following processes are reported: a process for grinding down the encysted Haematococcus after a preliminary drying with liquid nitrogen (WO89/06910), a process for rupturing the cell walls by freeze drying the encysted Haematococcus cells at a temperature below −50° C. followed by the addition of sodium chloride and comminuting the cells (French Patent Application No. 2,703,692), the recovery of astaxanthin carotenoid pigment from Haematococcus algae wherein the cell walls of algae are ruptured by the application of turbulent flow under a high pressure and the ruptured cell walls are dried and astaxanthins are extracted with an organic solvent (Japanese Patent Application Laid-Open No. Hei 9-111139) and a process for grinding Haematococcus in a dry encysted state to fine powders having an average particle size below 10 μm (Japanese Patent Application Kohyo No. Hei 02-503632). As a process for extracting a lipid containing astaxanthins from the ruptured alga which was obtained by these processes, a process is known for extracting it with an organic solvent such as ethanol, acetone, ether, chloroform, methylene chloride, hexane or the like, distilling off the solvent from the extract liquor to obtain an oil containing astaxanthins.
It became possible to supply an astaxanthins-containing Haematococcus alga in large quantities by a cultivation process, and consequently a problem occurred in the preservation management of Haematococcus alga until the extraction procedures of astaxanthin has been finished. Although Haematococcus algae themselves can be preserved stably by preserving them at low temperature, large-scale storage facilities are needed in order to preserve them in large quantities. Also, when large quantities of Haematococcus alga was subjected to rupture treatment, the resultant suspension (slurry) of ground Haematococcus caused a bad operability due to putrefaction. In this case, refrigeration facilities for preventing the putrefaction and maintenance and management costs for them are needed. As a result, these are not economical due to the complicated operations. Furthermore, there was a problem that the astaxanthin present in the ground Haematococcus alga degraded when contacted with oxygen, thus its content decreased.